/* Copyright Joyent, Inc. and other Node contributors.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to
 * deal in the Software without restriction, including without limitation the
 * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
 * sell copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 * IN THE SOFTWARE.
 */
#include "http_parser.h"
#include <assert.h>
#include <stddef.h>
#include <ctype.h>
#include <string.h>
#include <limits.h>

#ifndef ULLONG_MAX
#define ULLONG_MAX ((uint64_t)-1) /* 2^64-1 */
#endif

#ifndef MIN
#define MIN(a, b) ((a) < (b) ? (a) : (b))
#endif

#ifndef ARRAY_SIZE
#define ARRAY_SIZE(a) (sizeof(a) / sizeof((a)[0]))
#endif

#ifndef BIT_AT
#define BIT_AT(a, i) (!!((unsigned int)(a)[(unsigned int)(i) >> 3] & (1 << ((unsigned int)(i)&7))))
#endif

#ifndef ELEM_AT
#define ELEM_AT(a, i, v) ((unsigned int)(i) < ARRAY_SIZE(a) ? (a)[(i)] : (v))
#endif

#define SET_ERRNO(e) \
    do { \
        parser->http_errno = (e); \
    } while (0)

#define CURRENT_STATE() p_state
#define UPDATE_STATE(V) p_state = (enum state)(V);
#define RETURN(V) \
    do { \
        parser->state = CURRENT_STATE(); \
        return (V); \
    } while (0);
#define REEXECUTE() goto reexecute;

#ifdef __GNUC__
#define LIKELY(X)   __builtin_expect(!!(X), 1)
#define UNLIKELY(X) __builtin_expect(!!(X), 0)
#else
#define LIKELY(X)   (X)
#define UNLIKELY(X) (X)
#endif

/* Run the notify callback FOR, returning ER if it fails */
#define CALLBACK_NOTIFY_(FOR, ER) \
    do { \
        assert(HTTP_PARSER_ERRNO(parser) == HPE_OK); \
\
        if (LIKELY(settings->on_##FOR)) { \
            parser->state = CURRENT_STATE(); \
            if (UNLIKELY(0 != settings->on_##FOR(parser))) { \
                SET_ERRNO(HPE_CB_##FOR); \
            } \
            UPDATE_STATE(parser->state); \
\
            /* We either errored above or got paused; get out */ \
            if (UNLIKELY(HTTP_PARSER_ERRNO(parser) != HPE_OK)) { \
                return (ER); \
            } \
        } \
    } while (0)

/* Run the notify callback FOR and consume the current byte */
#define CALLBACK_NOTIFY(FOR) CALLBACK_NOTIFY_(FOR, p - data + 1)

/* Run the notify callback FOR and don't consume the current byte */
#define CALLBACK_NOTIFY_NOADVANCE(FOR) CALLBACK_NOTIFY_(FOR, p - data)

/* Run data callback FOR with LEN bytes, returning ER if it fails */
#define CALLBACK_DATA_(FOR, LEN, ER) \
    do { \
        assert(HTTP_PARSER_ERRNO(parser) == HPE_OK); \
\
        if (FOR##_mark) { \
            if (LIKELY(settings->on_##FOR)) { \
                parser->state = CURRENT_STATE(); \
                if (UNLIKELY(0 != settings->on_##FOR(parser, FOR##_mark, (LEN)))) { \
                    SET_ERRNO(HPE_CB_##FOR); \
                } \
                UPDATE_STATE(parser->state); \
\
                /* We either errored above or got paused; get out */ \
                if (UNLIKELY(HTTP_PARSER_ERRNO(parser) != HPE_OK)) { \
                    return (ER); \
                } \
            } \
            FOR##_mark = NULL; \
        } \
    } while (0)

/* Run the data callback FOR and consume the current byte */
#define CALLBACK_DATA(FOR) CALLBACK_DATA_(FOR, p - FOR##_mark, p - data + 1)

/* Run the data callback FOR and don't consume the current byte */
#define CALLBACK_DATA_NOADVANCE(FOR) CALLBACK_DATA_(FOR, p - FOR##_mark, p - data)

/* Set the mark FOR; non-destructive if mark is already set */
#define MARK(FOR) \
    do { \
        if (!FOR##_mark) { \
            FOR##_mark = p; \
        } \
    } while (0)

/* Don't allow the total size of the HTTP headers (including the status
 * line) to exceed HTTP_MAX_HEADER_SIZE.  This check is here to protect
 * embedders against denial-of-service attacks where the attacker feeds
 * us a never-ending header that the embedder keeps buffering.
 *
 * This check is arguably the responsibility of embedders but we're doing
 * it on the embedder's behalf because most won't bother and this way we
 * make the web a little safer.  HTTP_MAX_HEADER_SIZE is still far bigger
 * than any reasonable request or response so this should never affect
 * day-to-day operation.
 */
#define COUNT_HEADER_SIZE(V) \
    do { \
        parser->nread += (V); \
        if (UNLIKELY(parser->nread > (HTTP_MAX_HEADER_SIZE))) { \
            SET_ERRNO(HPE_HEADER_OVERFLOW); \
            goto error; \
        } \
    } while (0)

#define PROXY_CONNECTION  "proxy-connection"
#define CONNECTION        "connection"
#define CONTENT_LENGTH    "content-length"
#define TRANSFER_ENCODING "transfer-encoding"
#define UPGRADE           "upgrade"
#define CHUNKED           "chunked"
#define KEEP_ALIVE        "keep-alive"
#define CLOSE             "close"

static const char* method_strings[] = {
#define XX(num, name, string) #string,
    HTTP_METHOD_MAP(XX)
#undef XX
};

/* Tokens as defined by rfc 2616. Also lowercases them.
 *        token       = 1*<any CHAR except CTLs or separators>
 *     separators     = "(" | ")" | "<" | ">" | "@"
 *                    | "," | ";" | ":" | "\" | <">
 *                    | "/" | "[" | "]" | "?" | "="
 *                    | "{" | "}" | SP | HT
 */
static const char tokens[256] = {
    /*   0 nul    1 soh    2 stx    3 etx    4 eot    5 enq    6 ack    7 bel  */
    0, 0, 0, 0, 0, 0, 0, 0,
    /*   8 bs     9 ht    10 nl    11 vt    12 np    13 cr    14 so    15 si   */
    0, 0, 0, 0, 0, 0, 0, 0,
    /*  16 dle   17 dc1   18 dc2   19 dc3   20 dc4   21 nak   22 syn   23 etb */
    0, 0, 0, 0, 0, 0, 0, 0,
    /*  24 can   25 em    26 sub   27 esc   28 fs    29 gs    30 rs    31 us  */
    0, 0, 0, 0, 0, 0, 0, 0,
    /*  32 sp    33  !    34  "    35  #    36  $    37  %    38  &    39  '  */
    0, '!', 0, '#', '$', '%', '&', '\'',
    /*  40  (    41  )    42  *    43  +    44  ,    45  -    46  .    47  /  */
    0, 0, '*', '+', 0, '-', '.', 0,
    /*  48  0    49  1    50  2    51  3    52  4    53  5    54  6    55  7  */
    '0', '1', '2', '3', '4', '5', '6', '7',
    /*  56  8    57  9    58  :    59  ;    60  <    61  =    62  >    63  ?  */
    '8', '9', 0, 0, 0, 0, 0, 0,
    /*  64  @    65  A    66  B    67  C    68  D    69  E    70  F    71  G  */
    0, 'a', 'b', 'c', 'd', 'e', 'f', 'g',
    /*  72  H    73  I    74  J    75  K    76  L    77  M    78  N    79  O  */
    'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o',
    /*  80  P    81  Q    82  R    83  S    84  T    85  U    86  V    87  W  */
    'p', 'q', 'r', 's', 't', 'u', 'v', 'w',
    /*  88  X    89  Y    90  Z    91  [    92  \    93  ]    94  ^    95  _  */
    'x', 'y', 'z', 0, 0, 0, '^', '_',
    /*  96  `    97  a    98  b    99  c   100  d   101  e   102  f   103  g  */
    '`', 'a', 'b', 'c', 'd', 'e', 'f', 'g',
    /* 104  h   105  i   106  j   107  k   108  l   109  m   110  n   111  o  */
    'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o',
    /* 112  p   113  q   114  r   115  s   116  t   117  u   118  v   119  w  */
    'p', 'q', 'r', 's', 't', 'u', 'v', 'w',
    /* 120  x   121  y   122  z   123  {   124  |   125  }   126  ~   127 del */
    'x', 'y', 'z', 0, '|', 0, '~', 0};

static const int8_t unhex[256] = {-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
                                  -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 0,  1,  2,  3,
                                  4,  5,  6,  7,  8,  9,  -1, -1, -1, -1, -1, -1, -1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1,
                                  -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 10, 11, 12, 13, 14, 15, -1,
                                  -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1};

#if HTTP_PARSER_STRICT
#define T(v) 0
#else
#define T(v) v
#endif

static const uint8_t normal_url_char[32] = {
    /*   0 nul    1 soh    2 stx    3 etx    4 eot    5 enq    6 ack    7 bel  */
    0 | 0 | 0 | 0 | 0 | 0 | 0 | 0,
    /*   8 bs     9 ht    10 nl    11 vt    12 np    13 cr    14 so    15 si   */
    0 | T(2) | 0 | 0 | T(16) | 0 | 0 | 0,
    /*  16 dle   17 dc1   18 dc2   19 dc3   20 dc4   21 nak   22 syn   23 etb */
    0 | 0 | 0 | 0 | 0 | 0 | 0 | 0,
    /*  24 can   25 em    26 sub   27 esc   28 fs    29 gs    30 rs    31 us  */
    0 | 0 | 0 | 0 | 0 | 0 | 0 | 0,
    /*  32 sp    33  !    34  "    35  #    36  $    37  %    38  &    39  '  */
    0 | 2 | 4 | 0 | 16 | 32 | 64 | 128,
    /*  40  (    41  )    42  *    43  +    44  ,    45  -    46  .    47  /  */
    1 | 2 | 4 | 8 | 16 | 32 | 64 | 128,
    /*  48  0    49  1    50  2    51  3    52  4    53  5    54  6    55  7  */
    1 | 2 | 4 | 8 | 16 | 32 | 64 | 128,
    /*  56  8    57  9    58  :    59  ;    60  <    61  =    62  >    63  ?  */
    1 | 2 | 4 | 8 | 16 | 32 | 64 | 0,
    /*  64  @    65  A    66  B    67  C    68  D    69  E    70  F    71  G  */
    1 | 2 | 4 | 8 | 16 | 32 | 64 | 128,
    /*  72  H    73  I    74  J    75  K    76  L    77  M    78  N    79  O  */
    1 | 2 | 4 | 8 | 16 | 32 | 64 | 128,
    /*  80  P    81  Q    82  R    83  S    84  T    85  U    86  V    87  W  */
    1 | 2 | 4 | 8 | 16 | 32 | 64 | 128,
    /*  88  X    89  Y    90  Z    91  [    92  \    93  ]    94  ^    95  _  */
    1 | 2 | 4 | 8 | 16 | 32 | 64 | 128,
    /*  96  `    97  a    98  b    99  c   100  d   101  e   102  f   103  g  */
    1 | 2 | 4 | 8 | 16 | 32 | 64 | 128,
    /* 104  h   105  i   106  j   107  k   108  l   109  m   110  n   111  o  */
    1 | 2 | 4 | 8 | 16 | 32 | 64 | 128,
    /* 112  p   113  q   114  r   115  s   116  t   117  u   118  v   119  w  */
    1 | 2 | 4 | 8 | 16 | 32 | 64 | 128,
    /* 120  x   121  y   122  z   123  {   124  |   125  }   126  ~   127 del */
    1 | 2 | 4 | 8 | 16 | 32 | 64 | 0,
};

#undef T

enum state {
    s_dead = 1 /* important that this is > 0 */

    ,
    s_start_req_or_res,
    s_res_or_resp_H,
    s_start_res,
    s_res_H,
    s_res_HT,
    s_res_HTT,
    s_res_HTTP,
    s_res_http_major,
    s_res_http_dot,
    s_res_http_minor,
    s_res_http_end,
    s_res_first_status_code,
    s_res_status_code,
    s_res_status_start,
    s_res_status,
    s_res_line_almost_done

    ,
    s_start_req

    ,
    s_req_method,
    s_req_spaces_before_url,
    s_req_schema,
    s_req_schema_slash,
    s_req_schema_slash_slash,
    s_req_server_start,
    s_req_server,
    s_req_server_with_at,
    s_req_path,
    s_req_query_string_start,
    s_req_query_string,
    s_req_fragment_start,
    s_req_fragment,
    s_req_http_start,
    s_req_http_H,
    s_req_http_HT,
    s_req_http_HTT,
    s_req_http_HTTP,
    s_req_http_major,
    s_req_http_dot,
    s_req_http_minor,
    s_req_http_end,
    s_req_line_almost_done

    ,
    s_header_field_start,
    s_header_field,
    s_header_value_discard_ws,
    s_header_value_discard_ws_almost_done,
    s_header_value_discard_lws,
    s_header_value_start,
    s_header_value,
    s_header_value_lws

    ,
    s_header_almost_done

    ,
    s_chunk_size_start,
    s_chunk_size,
    s_chunk_parameters,
    s_chunk_size_almost_done

    ,
    s_headers_almost_done,
    s_headers_done

    /* Important: 's_headers_done' must be the last 'header' state. All
     * states beyond this must be 'body' states. It is used for overflow
     * checking. See the PARSING_HEADER() macro.
     */

    ,
    s_chunk_data,
    s_chunk_data_almost_done,
    s_chunk_data_done

    ,
    s_body_identity,
    s_body_identity_eof

    ,
    s_message_done
};

#define PARSING_HEADER(state) (state <= s_headers_done)

enum header_states {
    h_general = 0,
    h_C,
    h_CO,
    h_CON

    ,
    h_matching_connection,
    h_matching_proxy_connection,
    h_matching_content_length,
    h_matching_transfer_encoding,
    h_matching_upgrade

    ,
    h_connection,
    h_content_length,
    h_content_length_num,
    h_content_length_ws,
    h_transfer_encoding,
    h_upgrade

    ,
    h_matching_transfer_encoding_chunked,
    h_matching_connection_token_start,
    h_matching_connection_keep_alive,
    h_matching_connection_close,
    h_matching_connection_upgrade,
    h_matching_connection_token

    ,
    h_transfer_encoding_chunked,
    h_connection_keep_alive,
    h_connection_close,
    h_connection_upgrade
};

enum http_host_state {
    s_http_host_dead = 1,
    s_http_userinfo_start,
    s_http_userinfo,
    s_http_host_start,
    s_http_host_v6_start,
    s_http_host,
    s_http_host_v6,
    s_http_host_v6_end,
    s_http_host_v6_zone_start,
    s_http_host_v6_zone,
    s_http_host_port_start,
    s_http_host_port
};

/* Macros for character classes; depends on strict-mode  */
#define CR             '\r'
#define LF             '\n'
#define LOWER(c)       (unsigned char)(c | 0x20)
#define IS_ALPHA(c)    (LOWER(c) >= 'a' && LOWER(c) <= 'z')
#define IS_NUM(c)      ((c) >= '0' && (c) <= '9')
#define IS_ALPHANUM(c) (IS_ALPHA(c) || IS_NUM(c))
#define IS_HEX(c)      (IS_NUM(c) || (LOWER(c) >= 'a' && LOWER(c) <= 'f'))
#define IS_MARK(c)     ((c) == '-' || (c) == '_' || (c) == '.' || (c) == '!' || (c) == '~' || (c) == '*' || (c) == '\'' || (c) == '(' || (c) == ')')
#define IS_USERINFO_CHAR(c) \
    (IS_ALPHANUM(c) || IS_MARK(c) || (c) == '%' || (c) == ';' || (c) == ':' || (c) == '&' || (c) == '=' || (c) == '+' || (c) == '$' || (c) == ',')

#define STRICT_TOKEN(c) (tokens[(unsigned char)c])

#if HTTP_PARSER_STRICT
#define TOKEN(c)        (tokens[(unsigned char)c])
#define IS_URL_CHAR(c)  (BIT_AT(normal_url_char, (unsigned char)c))
#define IS_HOST_CHAR(c) (IS_ALPHANUM(c) || (c) == '.' || (c) == '-')
#else
#define TOKEN(c)        ((c == ' ') ? ' ' : tokens[(unsigned char)c])
#define IS_URL_CHAR(c)  (BIT_AT(normal_url_char, (unsigned char)c) || ((c)&0x80))
#define IS_HOST_CHAR(c) (IS_ALPHANUM(c) || (c) == '.' || (c) == '-' || (c) == '_')
#endif

/**
 * Verify that a char is a valid visible (printable) US-ASCII
 * character or %x80-FF
 **/
#define IS_HEADER_CHAR(ch) (ch == CR || ch == LF || ch == 9 || ((unsigned char)ch > 31 && ch != 127))

#define start_state (parser->type == HTTP_REQUEST ? s_start_req : s_start_res)

#if HTTP_PARSER_STRICT
#define STRICT_CHECK(cond) \
    do { \
        if (cond) { \
            SET_ERRNO(HPE_STRICT); \
            goto error; \
        } \
    } while (0)
#define NEW_MESSAGE() (http_should_keep_alive(parser) ? start_state : s_dead)
#else
#define STRICT_CHECK(cond)
#define NEW_MESSAGE() start_state
#endif

/* Map errno values to strings for human-readable output */
#define HTTP_STRERROR_GEN(n, s) {"HPE_" #n, s},
static struct {
    const char* name;
    const char* description;
} http_strerror_tab[] = {HTTP_ERRNO_MAP(HTTP_STRERROR_GEN)};
#undef HTTP_STRERROR_GEN

int http_message_needs_eof(const http_parser* parser);

/* Our URL parser.
 *
 * This is designed to be shared by http_parser_execute() for URL validation,
 * hence it has a state transition + byte-for-byte interface. In addition, it
 * is meant to be embedded in http_parser_parse_url(), which does the dirty
 * work of turning state transitions URL components for its API.
 *
 * This function should only be invoked with non-space characters. It is
 * assumed that the caller cares about (and can detect) the transition between
 * URL and non-URL states by looking for these.
 */
static enum state parse_url_char(enum state s, const char ch)
{
    if (ch == ' ' || ch == '\r' || ch == '\n') {
        return s_dead;
    }

#if HTTP_PARSER_STRICT
    if (ch == '\t' || ch == '\f') {
        return s_dead;
    }
#endif

    switch (s) {
    case s_req_spaces_before_url:
        /* Proxied requests are followed by scheme of an absolute URI (alpha).
         * All methods except CONNECT are followed by '/' or '*'.
         */

        if (ch == '/' || ch == '*') {
            return s_req_path;
        }

        if (IS_ALPHA(ch)) {
            return s_req_schema;
        }

        break;

    case s_req_schema:
        if (IS_ALPHA(ch)) {
            return s;
        }

        if (ch == ':') {
            return s_req_schema_slash;
        }

        break;

    case s_req_schema_slash:
        if (ch == '/') {
            return s_req_schema_slash_slash;
        }

        break;

    case s_req_schema_slash_slash:
        if (ch == '/') {
            return s_req_server_start;
        }

        break;

    case s_req_server_with_at:
        if (ch == '@') {
            return s_dead;
        }

    /* FALLTHROUGH */
    case s_req_server_start:
    case s_req_server:
        if (ch == '/') {
            return s_req_path;
        }

        if (ch == '?') {
            return s_req_query_string_start;
        }

        if (ch == '@') {
            return s_req_server_with_at;
        }

        if (IS_USERINFO_CHAR(ch) || ch == '[' || ch == ']') {
            return s_req_server;
        }

        break;

    case s_req_path:
        if (IS_URL_CHAR(ch)) {
            return s;
        }

        switch (ch) {
        case '?':
            return s_req_query_string_start;

        case '#':
            return s_req_fragment_start;
        }

        break;

    case s_req_query_string_start:
    case s_req_query_string:
        if (IS_URL_CHAR(ch)) {
            return s_req_query_string;
        }

        switch (ch) {
        case '?':
            /* allow extra '?' in query string */
            return s_req_query_string;

        case '#':
            return s_req_fragment_start;
        }

        break;

    case s_req_fragment_start:
        if (IS_URL_CHAR(ch)) {
            return s_req_fragment;
        }

        switch (ch) {
        case '?':
            return s_req_fragment;

        case '#':
            return s;
        }

        break;

    case s_req_fragment:
        if (IS_URL_CHAR(ch)) {
            return s;
        }

        switch (ch) {
        case '?':
        case '#':
            return s;
        }

        break;

    default:
        break;
    }

    /* We should never fall out of the switch above unless there's an error */
    return s_dead;
}

size_t http_parser_execute(http_parser* parser, const http_parser_settings* settings, const char* data, size_t len)
{
    char c, ch;
    int8_t unhex_val;
    const char* p = data;
    const char* header_field_mark = 0;
    const char* header_value_mark = 0;
    const char* url_mark = 0;
    const char* body_mark = 0;
    const char* status_mark = 0;
    enum state p_state = (enum state)parser->state;
    const unsigned int lenient = parser->lenient_http_headers;

    /* We're in an error state. Don't bother doing anything. */
    if (HTTP_PARSER_ERRNO(parser) != HPE_OK) {
        return 0;
    }

    if (len == 0) {
        switch (CURRENT_STATE()) {
        case s_body_identity_eof:
            /* Use of CALLBACK_NOTIFY() here would erroneously return 1 byte read if
             * we got paused.
             */
            CALLBACK_NOTIFY_NOADVANCE(message_complete);
            return 0;

        case s_dead:
        case s_start_req_or_res:
        case s_start_res:
        case s_start_req:
            return 0;

        default:
            SET_ERRNO(HPE_INVALID_EOF_STATE);
            return 1;
        }
    }

    if (CURRENT_STATE() == s_header_field)
        header_field_mark = data;
    if (CURRENT_STATE() == s_header_value)
        header_value_mark = data;
    switch (CURRENT_STATE()) {
    case s_req_path:
    case s_req_schema:
    case s_req_schema_slash:
    case s_req_schema_slash_slash:
    case s_req_server_start:
    case s_req_server:
    case s_req_server_with_at:
    case s_req_query_string_start:
    case s_req_query_string:
    case s_req_fragment_start:
    case s_req_fragment:
        url_mark = data;
        break;
    case s_res_status:
        status_mark = data;
        break;
    default:
        break;
    }

    for (p = data; p != data + len; p++) {
        ch = *p;

        if (PARSING_HEADER(CURRENT_STATE()))
            COUNT_HEADER_SIZE(1);

    reexecute:
        switch (CURRENT_STATE()) {
        case s_dead:
            /* this state is used after a 'Connection: close' message
             * the parser will error out if it reads another message
             */
            if (LIKELY(ch == CR || ch == LF))
                break;

            SET_ERRNO(HPE_CLOSED_CONNECTION);
            goto error;

        case s_start_req_or_res: {
            if (ch == CR || ch == LF)
                break;
            parser->flags = 0;
            parser->content_length = ULLONG_MAX;

            if (ch == 'H') {
                UPDATE_STATE(s_res_or_resp_H);

                CALLBACK_NOTIFY(message_begin);
            } else {
                parser->type = HTTP_REQUEST;
                UPDATE_STATE(s_start_req);
                REEXECUTE();
            }

            break;
        }

        case s_res_or_resp_H:
            if (ch == 'T') {
                parser->type = HTTP_RESPONSE;
                UPDATE_STATE(s_res_HT);
            } else {
                if (UNLIKELY(ch != 'E')) {
                    SET_ERRNO(HPE_INVALID_CONSTANT);
                    goto error;
                }

                parser->type = HTTP_REQUEST;
                parser->method = HTTP_HEAD;
                parser->index = 2;
                UPDATE_STATE(s_req_method);
            }
            break;

        case s_start_res: {
            parser->flags = 0;
            parser->content_length = ULLONG_MAX;

            switch (ch) {
            case 'H':
                UPDATE_STATE(s_res_H);
                break;

            case CR:
            case LF:
                break;

            default:
                SET_ERRNO(HPE_INVALID_CONSTANT);
                goto error;
            }

            CALLBACK_NOTIFY(message_begin);
            break;
        }

        case s_res_H:
            STRICT_CHECK(ch != 'T');
            UPDATE_STATE(s_res_HT);
            break;

        case s_res_HT:
            STRICT_CHECK(ch != 'T');
            UPDATE_STATE(s_res_HTT);
            break;

        case s_res_HTT:
            STRICT_CHECK(ch != 'P');
            UPDATE_STATE(s_res_HTTP);
            break;

        case s_res_HTTP:
            STRICT_CHECK(ch != '/');
            UPDATE_STATE(s_res_http_major);
            break;

        case s_res_http_major:
            if (UNLIKELY(!IS_NUM(ch))) {
                SET_ERRNO(HPE_INVALID_VERSION);
                goto error;
            }

            parser->http_major = ch - '0';
            UPDATE_STATE(s_res_http_dot);
            break;

        case s_res_http_dot: {
            if (UNLIKELY(ch != '.')) {
                SET_ERRNO(HPE_INVALID_VERSION);
                goto error;
            }

            UPDATE_STATE(s_res_http_minor);
            break;
        }

        case s_res_http_minor:
            if (UNLIKELY(!IS_NUM(ch))) {
                SET_ERRNO(HPE_INVALID_VERSION);
                goto error;
            }

            parser->http_minor = ch - '0';
            UPDATE_STATE(s_res_http_end);
            break;

        case s_res_http_end: {
            if (UNLIKELY(ch != ' ')) {
                SET_ERRNO(HPE_INVALID_VERSION);
                goto error;
            }

            UPDATE_STATE(s_res_first_status_code);
            break;
        }

        case s_res_first_status_code: {
            if (!IS_NUM(ch)) {
                if (ch == ' ') {
                    break;
                }

                SET_ERRNO(HPE_INVALID_STATUS);
                goto error;
            }
            parser->status_code = ch - '0';
            UPDATE_STATE(s_res_status_code);
            break;
        }

        case s_res_status_code: {
            if (!IS_NUM(ch)) {
                switch (ch) {
                case ' ':
                    UPDATE_STATE(s_res_status_start);
                    break;
                case CR:
                case LF:
                    UPDATE_STATE(s_res_status_start);
                    REEXECUTE();
                    break;
                default:
                    SET_ERRNO(HPE_INVALID_STATUS);
                    goto error;
                }
                break;
            }

            parser->status_code *= 10;
            parser->status_code += ch - '0';

            if (UNLIKELY(parser->status_code > 999)) {
                SET_ERRNO(HPE_INVALID_STATUS);
                goto error;
            }

            break;
        }

        case s_res_status_start: {
            MARK(status);
            UPDATE_STATE(s_res_status);
            parser->index = 0;

            if (ch == CR || ch == LF)
                REEXECUTE();

            break;
        }

        case s_res_status:
            if (ch == CR) {
                UPDATE_STATE(s_res_line_almost_done);
                CALLBACK_DATA(status);
                break;
            }

            if (ch == LF) {
                UPDATE_STATE(s_header_field_start);
                CALLBACK_DATA(status);
                break;
            }

            break;

        case s_res_line_almost_done:
            STRICT_CHECK(ch != LF);
            UPDATE_STATE(s_header_field_start);
            break;

        case s_start_req: {
            if (ch == CR || ch == LF)
                break;
            parser->flags = 0;
            parser->content_length = ULLONG_MAX;

            if (UNLIKELY(!IS_ALPHA(ch))) {
                SET_ERRNO(HPE_INVALID_METHOD);
                goto error;
            }

            parser->method = (enum http_method)0;
            parser->index = 1;
            switch (ch) {
            case 'A':
                parser->method = HTTP_ACL;
                break;
            case 'B':
                parser->method = HTTP_BIND;
                break;
            case 'C':
                parser->method = HTTP_CONNECT; /* or COPY, CHECKOUT */
                break;
            case 'D':
                parser->method = HTTP_DELETE;
                break;
            case 'G':
                parser->method = HTTP_GET;
                break;
            case 'H':
                parser->method = HTTP_HEAD;
                break;
            case 'L':
                parser->method = HTTP_LOCK; /* or LINK */
                break;
            case 'M':
                parser->method = HTTP_MKCOL; /* or MOVE, MKACTIVITY, MERGE, M-SEARCH, MKCALENDAR */
                break;
            case 'N':
                parser->method = HTTP_NOTIFY;
                break;
            case 'O':
                parser->method = HTTP_OPTIONS;
                break;
            case 'P':
                parser->method = HTTP_POST;
                /* or PROPFIND|PROPPATCH|PUT|PATCH|PURGE */
                break;
            case 'R':
                parser->method = HTTP_REPORT; /* or REBIND */
                break;
            case 'S':
                parser->method = HTTP_SUBSCRIBE; /* or SEARCH, SOURCE */
                break;
            case 'T':
                parser->method = HTTP_TRACE;
                break;
            case 'U':
                parser->method = HTTP_UNLOCK; /* or UNSUBSCRIBE, UNBIND, UNLINK */
                break;
            default:
                SET_ERRNO(HPE_INVALID_METHOD);
                goto error;
            }
            UPDATE_STATE(s_req_method);

            CALLBACK_NOTIFY(message_begin);

            break;
        }

        case s_req_method: {
            const char* matcher;
            if (UNLIKELY(ch == '\0')) {
                SET_ERRNO(HPE_INVALID_METHOD);
                goto error;
            }

            matcher = method_strings[parser->method];
            if (ch == ' ' && matcher[parser->index] == '\0') {
                UPDATE_STATE(s_req_spaces_before_url);
            } else if (ch == matcher[parser->index]) {
                ; /* nada */
            } else if ((ch >= 'A' && ch <= 'Z') || ch == '-') {
                switch (parser->method << 16 | parser->index << 8 | ch) {
#define XX(meth, pos, ch, new_meth) \
    case (HTTP_##meth << 16 | pos << 8 | ch): \
        parser->method = HTTP_##new_meth; \
        break;

                    XX(POST, 1, 'U', PUT)
                    XX(POST, 1, 'A', PATCH)
                    XX(POST, 1, 'R', PROPFIND)
                    XX(PUT, 2, 'R', PURGE)
                    XX(CONNECT, 1, 'H', CHECKOUT)
                    XX(CONNECT, 2, 'P', COPY)
                    XX(MKCOL, 1, 'O', MOVE)
                    XX(MKCOL, 1, 'E', MERGE)
                    XX(MKCOL, 1, '-', MSEARCH)
                    XX(MKCOL, 2, 'A', MKACTIVITY)
                    XX(MKCOL, 3, 'A', MKCALENDAR)
                    XX(SUBSCRIBE, 1, 'E', SEARCH)
                    XX(SUBSCRIBE, 1, 'O', SOURCE)
                    XX(REPORT, 2, 'B', REBIND)
                    XX(PROPFIND, 4, 'P', PROPPATCH)
                    XX(LOCK, 1, 'I', LINK)
                    XX(UNLOCK, 2, 'S', UNSUBSCRIBE)
                    XX(UNLOCK, 2, 'B', UNBIND)
                    XX(UNLOCK, 3, 'I', UNLINK)
#undef XX
                default:
                    SET_ERRNO(HPE_INVALID_METHOD);
                    goto error;
                }
            } else {
                SET_ERRNO(HPE_INVALID_METHOD);
                goto error;
            }

            ++parser->index;
            break;
        }

        case s_req_spaces_before_url: {
            if (ch == ' ')
                break;

            MARK(url);
            if (parser->method == HTTP_CONNECT) {
                UPDATE_STATE(s_req_server_start);
            }

            UPDATE_STATE(parse_url_char(CURRENT_STATE(), ch));
            if (UNLIKELY(CURRENT_STATE() == s_dead)) {
                SET_ERRNO(HPE_INVALID_URL);
                goto error;
            }

            break;
        }

        case s_req_schema:
        case s_req_schema_slash:
        case s_req_schema_slash_slash:
        case s_req_server_start: {
            switch (ch) {
            /* No whitespace allowed here */
            case ' ':
            case CR:
            case LF:
                SET_ERRNO(HPE_INVALID_URL);
                goto error;
            default:
                UPDATE_STATE(parse_url_char(CURRENT_STATE(), ch));
                if (UNLIKELY(CURRENT_STATE() == s_dead)) {
                    SET_ERRNO(HPE_INVALID_URL);
                    goto error;
                }
            }

            break;
        }

        case s_req_server:
        case s_req_server_with_at:
        case s_req_path:
        case s_req_query_string_start:
        case s_req_query_string:
        case s_req_fragment_start:
        case s_req_fragment: {
            switch (ch) {
            case ' ':
                UPDATE_STATE(s_req_http_start);
                CALLBACK_DATA(url);
                break;
            case CR:
            case LF:
                parser->http_major = 0;
                parser->http_minor = 9;
                UPDATE_STATE((ch == CR) ? s_req_line_almost_done : s_header_field_start);
                CALLBACK_DATA(url);
                break;
            default:
                UPDATE_STATE(parse_url_char(CURRENT_STATE(), ch));
                if (UNLIKELY(CURRENT_STATE() == s_dead)) {
                    SET_ERRNO(HPE_INVALID_URL);
                    goto error;
                }
            }
            break;
        }

        case s_req_http_start:
            switch (ch) {
            case 'H':
                UPDATE_STATE(s_req_http_H);
                break;
            case ' ':
                break;
            default:
                SET_ERRNO(HPE_INVALID_CONSTANT);
                goto error;
            }
            break;

        case s_req_http_H:
            STRICT_CHECK(ch != 'T');
            UPDATE_STATE(s_req_http_HT);
            break;

        case s_req_http_HT:
            STRICT_CHECK(ch != 'T');
            UPDATE_STATE(s_req_http_HTT);
            break;

        case s_req_http_HTT:
            STRICT_CHECK(ch != 'P');
            UPDATE_STATE(s_req_http_HTTP);
            break;

        case s_req_http_HTTP:
            STRICT_CHECK(ch != '/');
            UPDATE_STATE(s_req_http_major);
            break;

        case s_req_http_major:
            if (UNLIKELY(!IS_NUM(ch))) {
                SET_ERRNO(HPE_INVALID_VERSION);
                goto error;
            }

            parser->http_major = ch - '0';
            UPDATE_STATE(s_req_http_dot);
            break;

        case s_req_http_dot: {
            if (UNLIKELY(ch != '.')) {
                SET_ERRNO(HPE_INVALID_VERSION);
                goto error;
            }

            UPDATE_STATE(s_req_http_minor);
            break;
        }

        case s_req_http_minor:
            if (UNLIKELY(!IS_NUM(ch))) {
                SET_ERRNO(HPE_INVALID_VERSION);
                goto error;
            }

            parser->http_minor = ch - '0';
            UPDATE_STATE(s_req_http_end);
            break;

        case s_req_http_end: {
            if (ch == CR) {
                UPDATE_STATE(s_req_line_almost_done);
                break;
            }

            if (ch == LF) {
                UPDATE_STATE(s_header_field_start);
                break;
            }

            SET_ERRNO(HPE_INVALID_VERSION);
            goto error;
            break;
        }

        /* end of request line */
        case s_req_line_almost_done: {
            if (UNLIKELY(ch != LF)) {
                SET_ERRNO(HPE_LF_EXPECTED);
                goto error;
            }

            UPDATE_STATE(s_header_field_start);
            break;
        }

        case s_header_field_start: {
            if (ch == CR) {
                UPDATE_STATE(s_headers_almost_done);
                break;
            }

            if (ch == LF) {
                /* they might be just sending \n instead of \r\n so this would be
                 * the second \n to denote the end of headers*/
                UPDATE_STATE(s_headers_almost_done);
                REEXECUTE();
            }

            c = TOKEN(ch);

            if (UNLIKELY(!c)) {
                SET_ERRNO(HPE_INVALID_HEADER_TOKEN);
                goto error;
            }

            MARK(header_field);

            parser->index = 0;
            UPDATE_STATE(s_header_field);

            switch (c) {
            case 'c':
                parser->header_state = h_C;
                break;

            case 'p':
                parser->header_state = h_matching_proxy_connection;
                break;

            case 't':
                parser->header_state = h_matching_transfer_encoding;
                break;

            case 'u':
                parser->header_state = h_matching_upgrade;
                break;

            default:
                parser->header_state = h_general;
                break;
            }
            break;
        }

        case s_header_field: {
            const char* start = p;
            for (; p != data + len; p++) {
                ch = *p;
                c = TOKEN(ch);

                if (!c)
                    break;

                switch (parser->header_state) {
                case h_general:
                    break;

                case h_C:
                    parser->index++;
                    parser->header_state = (c == 'o' ? h_CO : h_general);
                    break;

                case h_CO:
                    parser->index++;
                    parser->header_state = (c == 'n' ? h_CON : h_general);
                    break;

                case h_CON:
                    parser->index++;
                    switch (c) {
                    case 'n':
                        parser->header_state = h_matching_connection;
                        break;
                    case 't':
                        parser->header_state = h_matching_content_length;
                        break;
                    default:
                        parser->header_state = h_general;
                        break;
                    }
                    break;

                    /* connection */

                case h_matching_connection:
                    parser->index++;
                    if (parser->index > sizeof(CONNECTION) - 1 || c != CONNECTION[parser->index]) {
                        parser->header_state = h_general;
                    } else if (parser->index == sizeof(CONNECTION) - 2) {
                        parser->header_state = h_connection;
                    }
                    break;

                    /* proxy-connection */

                case h_matching_proxy_connection:
                    parser->index++;
                    if (parser->index > sizeof(PROXY_CONNECTION) - 1 || c != PROXY_CONNECTION[parser->index]) {
                        parser->header_state = h_general;
                    } else if (parser->index == sizeof(PROXY_CONNECTION) - 2) {
                        parser->header_state = h_connection;
                    }
                    break;

                    /* content-length */

                case h_matching_content_length:
                    parser->index++;
                    if (parser->index > sizeof(CONTENT_LENGTH) - 1 || c != CONTENT_LENGTH[parser->index]) {
                        parser->header_state = h_general;
                    } else if (parser->index == sizeof(CONTENT_LENGTH) - 2) {
                        parser->header_state = h_content_length;
                    }
                    break;

                    /* transfer-encoding */

                case h_matching_transfer_encoding:
                    parser->index++;
                    if (parser->index > sizeof(TRANSFER_ENCODING) - 1 || c != TRANSFER_ENCODING[parser->index]) {
                        parser->header_state = h_general;
                    } else if (parser->index == sizeof(TRANSFER_ENCODING) - 2) {
                        parser->header_state = h_transfer_encoding;
                    }
                    break;

                    /* upgrade */

                case h_matching_upgrade:
                    parser->index++;
                    if (parser->index > sizeof(UPGRADE) - 1 || c != UPGRADE[parser->index]) {
                        parser->header_state = h_general;
                    } else if (parser->index == sizeof(UPGRADE) - 2) {
                        parser->header_state = h_upgrade;
                    }
                    break;

                case h_connection:
                case h_content_length:
                case h_transfer_encoding:
                case h_upgrade:
                    if (ch != ' ')
                        parser->header_state = h_general;
                    break;

                default:
                    assert(0 && "Unknown header_state");
                    break;
                }
            }

            COUNT_HEADER_SIZE(p - start);

            if (p == data + len) {
                --p;
                break;
            }

            if (ch == ':') {
                UPDATE_STATE(s_header_value_discard_ws);
                CALLBACK_DATA(header_field);
                break;
            }

            SET_ERRNO(HPE_INVALID_HEADER_TOKEN);
            goto error;
        }

        case s_header_value_discard_ws:
            if (ch == ' ' || ch == '\t')
                break;

            if (ch == CR) {
                UPDATE_STATE(s_header_value_discard_ws_almost_done);
                break;
            }

            if (ch == LF) {
                UPDATE_STATE(s_header_value_discard_lws);
                break;
            }

            /* FALLTHROUGH */

        case s_header_value_start: {
            MARK(header_value);

            UPDATE_STATE(s_header_value);
            parser->index = 0;

            c = LOWER(ch);

            switch (parser->header_state) {
            case h_upgrade:
                parser->flags |= F_UPGRADE;
                parser->header_state = h_general;
                break;

            case h_transfer_encoding:
                /* looking for 'Transfer-Encoding: chunked' */
                if ('c' == c) {
                    parser->header_state = h_matching_transfer_encoding_chunked;
                } else {
                    parser->header_state = h_general;
                }
                break;

            case h_content_length:
                if (UNLIKELY(!IS_NUM(ch))) {
                    SET_ERRNO(HPE_INVALID_CONTENT_LENGTH);
                    goto error;
                }

                if (parser->flags & F_CONTENTLENGTH) {
                    SET_ERRNO(HPE_UNEXPECTED_CONTENT_LENGTH);
                    goto error;
                }

                parser->flags |= F_CONTENTLENGTH;
                parser->content_length = ch - '0';
                parser->header_state = h_content_length_num;
                break;

            case h_connection:
                /* looking for 'Connection: keep-alive' */
                if (c == 'k') {
                    parser->header_state = h_matching_connection_keep_alive;
                    /* looking for 'Connection: close' */
                } else if (c == 'c') {
                    parser->header_state = h_matching_connection_close;
                } else if (c == 'u') {
                    parser->header_state = h_matching_connection_upgrade;
                } else {
                    parser->header_state = h_matching_connection_token;
                }
                break;

            /* Multi-value `Connection` header */
            case h_matching_connection_token_start:
                break;

            default:
                parser->header_state = h_general;
                break;
            }
            break;
        }

        case s_header_value: {
            const char* start = p;
            enum header_states h_state = (enum header_states)parser->header_state;
            for (; p != data + len; p++) {
                ch = *p;
                if (ch == CR) {
                    UPDATE_STATE(s_header_almost_done);
                    parser->header_state = h_state;
                    CALLBACK_DATA(header_value);
                    break;
                }

                if (ch == LF) {
                    UPDATE_STATE(s_header_almost_done);
                    COUNT_HEADER_SIZE(p - start);
                    parser->header_state = h_state;
                    CALLBACK_DATA_NOADVANCE(header_value);
                    REEXECUTE();
                }

                if (!lenient && !IS_HEADER_CHAR(ch)) {
                    SET_ERRNO(HPE_INVALID_HEADER_TOKEN);
                    goto error;
                }

                c = LOWER(ch);

                switch (h_state) {
                case h_general: {
                    const char* p_cr;
                    const char* p_lf;
                    size_t limit = data + len - p;

                    limit = MIN(limit, HTTP_MAX_HEADER_SIZE);

                    p_cr = (const char*)memchr(p, CR, limit);
                    p_lf = (const char*)memchr(p, LF, limit);
                    if (p_cr != NULL) {
                        if (p_lf != NULL && p_cr >= p_lf)
                            p = p_lf;
                        else
                            p = p_cr;
                    } else if (UNLIKELY(p_lf != NULL)) {
                        p = p_lf;
                    } else {
                        p = data + len;
                    }
                    --p;

                    break;
                }

                case h_connection:
                case h_transfer_encoding:
                    assert(0 && "Shouldn't get here.");
                    break;

                case h_content_length:
                    if (ch == ' ')
                        break;
                    h_state = h_content_length_num;
                    /* FALLTHROUGH */

                case h_content_length_num: {
                    uint64_t t;

                    if (ch == ' ') {
                        h_state = h_content_length_ws;
                        break;
                    }

                    if (UNLIKELY(!IS_NUM(ch))) {
                        SET_ERRNO(HPE_INVALID_CONTENT_LENGTH);
                        parser->header_state = h_state;
                        goto error;
                    }

                    t = parser->content_length;
                    t *= 10;
                    t += ch - '0';

                    /* Overflow? Test against a conservative limit for simplicity. */
                    if (UNLIKELY((ULLONG_MAX - 10) / 10 < parser->content_length)) {
                        SET_ERRNO(HPE_INVALID_CONTENT_LENGTH);
                        parser->header_state = h_state;
                        goto error;
                    }

                    parser->content_length = t;
                    break;
                }

                case h_content_length_ws:
                    if (ch == ' ')
                        break;
                    SET_ERRNO(HPE_INVALID_CONTENT_LENGTH);
                    parser->header_state = h_state;
                    goto error;

                /* Transfer-Encoding: chunked */
                case h_matching_transfer_encoding_chunked:
                    parser->index++;
                    if (parser->index > sizeof(CHUNKED) - 1 || c != CHUNKED[parser->index]) {
                        h_state = h_general;
                    } else if (parser->index == sizeof(CHUNKED) - 2) {
                        h_state = h_transfer_encoding_chunked;
                    }
                    break;

                case h_matching_connection_token_start:
                    /* looking for 'Connection: keep-alive' */
                    if (c == 'k') {
                        h_state = h_matching_connection_keep_alive;
                        /* looking for 'Connection: close' */
                    } else if (c == 'c') {
                        h_state = h_matching_connection_close;
                    } else if (c == 'u') {
                        h_state = h_matching_connection_upgrade;
                    } else if (STRICT_TOKEN(c)) {
                        h_state = h_matching_connection_token;
                    } else if (c == ' ' || c == '\t') {
                        /* Skip lws */
                    } else {
                        h_state = h_general;
                    }
                    break;

                /* looking for 'Connection: keep-alive' */
                case h_matching_connection_keep_alive:
                    parser->index++;
                    if (parser->index > sizeof(KEEP_ALIVE) - 1 || c != KEEP_ALIVE[parser->index]) {
                        h_state = h_matching_connection_token;
                    } else if (parser->index == sizeof(KEEP_ALIVE) - 2) {
                        h_state = h_connection_keep_alive;
                    }
                    break;

                /* looking for 'Connection: close' */
                case h_matching_connection_close:
                    parser->index++;
                    if (parser->index > sizeof(CLOSE) - 1 || c != CLOSE[parser->index]) {
                        h_state = h_matching_connection_token;
                    } else if (parser->index == sizeof(CLOSE) - 2) {
                        h_state = h_connection_close;
                    }
                    break;

                /* looking for 'Connection: upgrade' */
                case h_matching_connection_upgrade:
                    parser->index++;
                    if (parser->index > sizeof(UPGRADE) - 1 || c != UPGRADE[parser->index]) {
                        h_state = h_matching_connection_token;
                    } else if (parser->index == sizeof(UPGRADE) - 2) {
                        h_state = h_connection_upgrade;
                    }
                    break;

                case h_matching_connection_token:
                    if (ch == ',') {
                        h_state = h_matching_connection_token_start;
                        parser->index = 0;
                    }
                    break;

                case h_transfer_encoding_chunked:
                    if (ch != ' ')
                        h_state = h_general;
                    break;

                case h_connection_keep_alive:
                case h_connection_close:
                case h_connection_upgrade:
                    if (ch == ',') {
                        if (h_state == h_connection_keep_alive) {
                            parser->flags |= F_CONNECTION_KEEP_ALIVE;
                        } else if (h_state == h_connection_close) {
                            parser->flags |= F_CONNECTION_CLOSE;
                        } else if (h_state == h_connection_upgrade) {
                            parser->flags |= F_CONNECTION_UPGRADE;
                        }
                        h_state = h_matching_connection_token_start;
                        parser->index = 0;
                    } else if (ch != ' ') {
                        h_state = h_matching_connection_token;
                    }
                    break;

                default:
                    UPDATE_STATE(s_header_value);
                    h_state = h_general;
                    break;
                }
            }
            parser->header_state = h_state;

            COUNT_HEADER_SIZE(p - start);

            if (p == data + len)
                --p;
            break;
        }

        case s_header_almost_done: {
            if (UNLIKELY(ch != LF)) {
                SET_ERRNO(HPE_LF_EXPECTED);
                goto error;
            }

            UPDATE_STATE(s_header_value_lws);
            break;
        }

        case s_header_value_lws: {
            if (ch == ' ' || ch == '\t') {
                UPDATE_STATE(s_header_value_start);
                REEXECUTE();
            }

            /* finished the header */
            switch (parser->header_state) {
            case h_connection_keep_alive:
                parser->flags |= F_CONNECTION_KEEP_ALIVE;
                break;
            case h_connection_close:
                parser->flags |= F_CONNECTION_CLOSE;
                break;
            case h_transfer_encoding_chunked:
                parser->flags |= F_CHUNKED;
                break;
            case h_connection_upgrade:
                parser->flags |= F_CONNECTION_UPGRADE;
                break;
            default:
                break;
            }

            UPDATE_STATE(s_header_field_start);
            REEXECUTE();
        }

        case s_header_value_discard_ws_almost_done: {
            STRICT_CHECK(ch != LF);
            UPDATE_STATE(s_header_value_discard_lws);
            break;
        }

        case s_header_value_discard_lws: {
            if (ch == ' ' || ch == '\t') {
                UPDATE_STATE(s_header_value_discard_ws);
                break;
            } else {
                switch (parser->header_state) {
                case h_connection_keep_alive:
                    parser->flags |= F_CONNECTION_KEEP_ALIVE;
                    break;
                case h_connection_close:
                    parser->flags |= F_CONNECTION_CLOSE;
                    break;
                case h_connection_upgrade:
                    parser->flags |= F_CONNECTION_UPGRADE;
                    break;
                case h_transfer_encoding_chunked:
                    parser->flags |= F_CHUNKED;
                    break;
                default:
                    break;
                }

                /* header value was empty */
                MARK(header_value);
                UPDATE_STATE(s_header_field_start);
                CALLBACK_DATA_NOADVANCE(header_value);
                REEXECUTE();
            }
        }

        case s_headers_almost_done: {
            STRICT_CHECK(ch != LF);

            if (parser->flags & F_TRAILING) {
                /* End of a chunked request */
                UPDATE_STATE(s_message_done);
                CALLBACK_NOTIFY_NOADVANCE(chunk_complete);
                REEXECUTE();
            }

            /* Cannot use chunked encoding and a content-length header together
               per the HTTP specification. */
            if ((parser->flags & F_CHUNKED) && (parser->flags & F_CONTENTLENGTH)) {
                SET_ERRNO(HPE_UNEXPECTED_CONTENT_LENGTH);
                goto error;
            }

            UPDATE_STATE(s_headers_done);

            /* Set this here so that on_headers_complete() callbacks can see it */
            if ((parser->flags & F_UPGRADE) && (parser->flags & F_CONNECTION_UPGRADE)) {
                /* For responses, "Upgrade: foo" and "Connection: upgrade" are
                 * mandatory only when it is a 101 Switching Protocols response,
                 * otherwise it is purely informational, to announce support.
                 */
                parser->upgrade = (parser->type == HTTP_REQUEST || parser->status_code == 101);
            } else {
                parser->upgrade = (parser->method == HTTP_CONNECT);
            }

            /* Here we call the headers_complete callback. This is somewhat
             * different than other callbacks because if the user returns 1, we
             * will interpret that as saying that this message has no body. This
             * is needed for the annoying case of recieving a response to a HEAD
             * request.
             *
             * We'd like to use CALLBACK_NOTIFY_NOADVANCE() here but we cannot, so
             * we have to simulate it by handling a change in errno below.
             */
            if (settings->on_headers_complete) {
                switch (settings->on_headers_complete(parser)) {
                case 0:
                    break;

                case 2:
                    parser->upgrade = 1;

                /* FALLTHROUGH */
                case 1:
                    parser->flags |= F_SKIPBODY;
                    break;

                default:
                    SET_ERRNO(HPE_CB_headers_complete);
                    RETURN(p - data); /* Error */
                }
            }

            if (HTTP_PARSER_ERRNO(parser) != HPE_OK) {
                RETURN(p - data);
            }

            REEXECUTE();
        }

        case s_headers_done: {
            int hasBody;
            STRICT_CHECK(ch != LF);

            parser->nread = 0;

            hasBody = parser->flags & F_CHUNKED || (parser->content_length > 0 && parser->content_length != ULLONG_MAX);
            if (parser->upgrade && (parser->method == HTTP_CONNECT || (parser->flags & F_SKIPBODY) || !hasBody)) {
                /* Exit, the rest of the message is in a different protocol. */
                UPDATE_STATE(NEW_MESSAGE());
                CALLBACK_NOTIFY(message_complete);
                RETURN((p - data) + 1);
            }

            if (parser->flags & F_SKIPBODY) {
                UPDATE_STATE(NEW_MESSAGE());
                CALLBACK_NOTIFY(message_complete);
            } else if (parser->flags & F_CHUNKED) {
                /* chunked encoding - ignore Content-Length header */
                UPDATE_STATE(s_chunk_size_start);
            } else {
                if (parser->content_length == 0) {
                    /* Content-Length header given but zero: Content-Length: 0\r\n */
                    UPDATE_STATE(NEW_MESSAGE());
                    CALLBACK_NOTIFY(message_complete);
                } else if (parser->content_length != ULLONG_MAX) {
                    /* Content-Length header given and non-zero */
                    UPDATE_STATE(s_body_identity);
                } else {
                    if (!http_message_needs_eof(parser)) {
                        /* Assume content-length 0 - read the next */
                        UPDATE_STATE(NEW_MESSAGE());
                        CALLBACK_NOTIFY(message_complete);
                    } else {
                        /* Read body until EOF */
                        UPDATE_STATE(s_body_identity_eof);
                    }
                }
            }

            break;
        }

        case s_body_identity: {
            uint64_t to_read = MIN(parser->content_length, (uint64_t)((data + len) - p));

            assert(parser->content_length != 0 && parser->content_length != ULLONG_MAX);

            /* The difference between advancing content_length and p is because
             * the latter will automaticaly advance on the next loop iteration.
             * Further, if content_length ends up at 0, we want to see the last
             * byte again for our message complete callback.
             */
            MARK(body);
            parser->content_length -= to_read;
            p += to_read - 1;

            if (parser->content_length == 0) {
                UPDATE_STATE(s_message_done);

                /* Mimic CALLBACK_DATA_NOADVANCE() but with one extra byte.
                 *
                 * The alternative to doing this is to wait for the next byte to
                 * trigger the data callback, just as in every other case. The
                 * problem with this is that this makes it difficult for the test
                 * harness to distinguish between complete-on-EOF and
                 * complete-on-length. It's not clear that this distinction is
                 * important for applications, but let's keep it for now.
                 */
                CALLBACK_DATA_(body, p - body_mark + 1, p - data);
                REEXECUTE();
            }

            break;
        }

        /* read until EOF */
        case s_body_identity_eof:
            MARK(body);
            p = data + len - 1;

            break;

        case s_message_done:
            UPDATE_STATE(NEW_MESSAGE());
            CALLBACK_NOTIFY(message_complete);
            if (parser->upgrade) {
                /* Exit, the rest of the message is in a different protocol. */
                RETURN((p - data) + 1);
            }
            break;

        case s_chunk_size_start: {
            assert(parser->nread == 1);
            assert(parser->flags & F_CHUNKED);

            unhex_val = unhex[(unsigned char)ch];
            if (UNLIKELY(unhex_val == -1)) {
                SET_ERRNO(HPE_INVALID_CHUNK_SIZE);
                goto error;
            }

            parser->content_length = unhex_val;
            UPDATE_STATE(s_chunk_size);
            break;
        }

        case s_chunk_size: {
            uint64_t t;

            assert(parser->flags & F_CHUNKED);

            if (ch == CR) {
                UPDATE_STATE(s_chunk_size_almost_done);
                break;
            }

            unhex_val = unhex[(unsigned char)ch];

            if (unhex_val == -1) {
                if (ch == ';' || ch == ' ') {
                    UPDATE_STATE(s_chunk_parameters);
                    break;
                }

                SET_ERRNO(HPE_INVALID_CHUNK_SIZE);
                goto error;
            }

            t = parser->content_length;
            t *= 16;
            t += unhex_val;

            /* Overflow? Test against a conservative limit for simplicity. */
            if (UNLIKELY((ULLONG_MAX - 16) / 16 < parser->content_length)) {
                SET_ERRNO(HPE_INVALID_CONTENT_LENGTH);
                goto error;
            }

            parser->content_length = t;
            break;
        }

        case s_chunk_parameters: {
            assert(parser->flags & F_CHUNKED);
            /* just ignore this shit. TODO check for overflow */
            if (ch == CR) {
                UPDATE_STATE(s_chunk_size_almost_done);
                break;
            }
            break;
        }

        case s_chunk_size_almost_done: {
            assert(parser->flags & F_CHUNKED);
            STRICT_CHECK(ch != LF);

            parser->nread = 0;

            if (parser->content_length == 0) {
                parser->flags |= F_TRAILING;
                UPDATE_STATE(s_header_field_start);
            } else {
                UPDATE_STATE(s_chunk_data);
            }
            CALLBACK_NOTIFY(chunk_header);
            break;
        }

        case s_chunk_data: {
            uint64_t to_read = MIN(parser->content_length, (uint64_t)((data + len) - p));

            assert(parser->flags & F_CHUNKED);
            assert(parser->content_length != 0 && parser->content_length != ULLONG_MAX);

            /* See the explanation in s_body_identity for why the content
             * length and data pointers are managed this way.
             */
            MARK(body);
            parser->content_length -= to_read;
            p += to_read - 1;

            if (parser->content_length == 0) {
                UPDATE_STATE(s_chunk_data_almost_done);
            }

            break;
        }

        case s_chunk_data_almost_done:
            assert(parser->flags & F_CHUNKED);
            assert(parser->content_length == 0);
            STRICT_CHECK(ch != CR);
            UPDATE_STATE(s_chunk_data_done);
            CALLBACK_DATA(body);
            break;

        case s_chunk_data_done:
            assert(parser->flags & F_CHUNKED);
            STRICT_CHECK(ch != LF);
            parser->nread = 0;
            UPDATE_STATE(s_chunk_size_start);
            CALLBACK_NOTIFY(chunk_complete);
            break;

        default:
            assert(0 && "unhandled state");
            SET_ERRNO(HPE_INVALID_INTERNAL_STATE);
            goto error;
        }
    }

    /* Run callbacks for any marks that we have leftover after we ran our of
     * bytes. There should be at most one of these set, so it's OK to invoke
     * them in series (unset marks will not result in callbacks).
     *
     * We use the NOADVANCE() variety of callbacks here because 'p' has already
     * overflowed 'data' and this allows us to correct for the off-by-one that
     * we'd otherwise have (since CALLBACK_DATA() is meant to be run with a 'p'
     * value that's in-bounds).
     */

    assert(((header_field_mark ? 1 : 0) + (header_value_mark ? 1 : 0) + (url_mark ? 1 : 0) + (body_mark ? 1 : 0) + (status_mark ? 1 : 0)) <= 1);

    CALLBACK_DATA_NOADVANCE(header_field);
    CALLBACK_DATA_NOADVANCE(header_value);
    CALLBACK_DATA_NOADVANCE(url);
    CALLBACK_DATA_NOADVANCE(body);
    CALLBACK_DATA_NOADVANCE(status);

    RETURN(len);

error:
    if (HTTP_PARSER_ERRNO(parser) == HPE_OK) {
        SET_ERRNO(HPE_UNKNOWN);
    }

    RETURN(p - data);
}

/* Does the parser need to see an EOF to find the end of the message? */
int http_message_needs_eof(const http_parser* parser)
{
    if (parser->type == HTTP_REQUEST) {
        return 0;
    }

    /* See RFC 2616 section 4.4 */
    if (parser->status_code / 100 == 1 || /* 1xx e.g. Continue */
        parser->status_code == 204 ||     /* No Content */
        parser->status_code == 304 ||     /* Not Modified */
        parser->flags & F_SKIPBODY) {     /* response to a HEAD request */
        return 0;
    }

    if ((parser->flags & F_CHUNKED) || parser->content_length != ULLONG_MAX) {
        return 0;
    }

    return 1;
}

int http_should_keep_alive(const http_parser* parser)
{
    if (parser->http_major > 0 && parser->http_minor > 0) {
        /* HTTP/1.1 */
        if (parser->flags & F_CONNECTION_CLOSE) {
            return 0;
        }
    } else {
        /* HTTP/1.0 or earlier */
        if (!(parser->flags & F_CONNECTION_KEEP_ALIVE)) {
            return 0;
        }
    }

    return !http_message_needs_eof(parser);
}

const char* http_method_str(enum http_method m)
{
    return ELEM_AT(method_strings, m, "<unknown>");
}

void http_parser_init(http_parser* parser, enum http_parser_type t)
{
    void* data = parser->data; /* preserve application data */
    memset(parser, 0, sizeof(*parser));
    parser->data = data;
    parser->type = t;
    parser->state = (t == HTTP_REQUEST ? s_start_req : (t == HTTP_RESPONSE ? s_start_res : s_start_req_or_res));
    parser->http_errno = HPE_OK;
}

void http_parser_settings_init(http_parser_settings* settings)
{
    memset(settings, 0, sizeof(*settings));
}

const char* http_errno_name(enum http_errno err)
{
    assert(((size_t)err) < ARRAY_SIZE(http_strerror_tab));
    return http_strerror_tab[err].name;
}

const char* http_errno_description(enum http_errno err)
{
    assert(((size_t)err) < ARRAY_SIZE(http_strerror_tab));
    return http_strerror_tab[err].description;
}

static enum http_host_state http_parse_host_char(enum http_host_state s, const char ch)
{
    switch (s) {
    case s_http_userinfo:
    case s_http_userinfo_start:
        if (ch == '@') {
            return s_http_host_start;
        }

        if (IS_USERINFO_CHAR(ch)) {
            return s_http_userinfo;
        }
        break;

    case s_http_host_start:
        if (ch == '[') {
            return s_http_host_v6_start;
        }

        if (IS_HOST_CHAR(ch)) {
            return s_http_host;
        }

        break;

    case s_http_host:
        if (IS_HOST_CHAR(ch)) {
            return s_http_host;
        }

    /* FALLTHROUGH */
    case s_http_host_v6_end:
        if (ch == ':') {
            return s_http_host_port_start;
        }

        break;

    case s_http_host_v6:
        if (ch == ']') {
            return s_http_host_v6_end;
        }

    /* FALLTHROUGH */
    case s_http_host_v6_start:
        if (IS_HEX(ch) || ch == ':' || ch == '.') {
            return s_http_host_v6;
        }

        if (s == s_http_host_v6 && ch == '%') {
            return s_http_host_v6_zone_start;
        }
        break;

    case s_http_host_v6_zone:
        if (ch == ']') {
            return s_http_host_v6_end;
        }

    /* FALLTHROUGH */
    case s_http_host_v6_zone_start:
        /* RFC 6874 Zone ID consists of 1*( unreserved / pct-encoded) */
        if (IS_ALPHANUM(ch) || ch == '%' || ch == '.' || ch == '-' || ch == '_' || ch == '~') {
            return s_http_host_v6_zone;
        }
        break;

    case s_http_host_port:
    case s_http_host_port_start:
        if (IS_NUM(ch)) {
            return s_http_host_port;
        }

        break;

    default:
        break;
    }
    return s_http_host_dead;
}

static int http_parse_host(const char* buf, struct http_parser_url* u, int found_at)
{
    enum http_host_state s;

    const char* p;
    size_t buflen = u->field_data[UF_HOST].off + u->field_data[UF_HOST].len;

    assert(u->field_set & (1 << UF_HOST));

    u->field_data[UF_HOST].len = 0;

    s = found_at ? s_http_userinfo_start : s_http_host_start;

    for (p = buf + u->field_data[UF_HOST].off; p < buf + buflen; p++) {
        enum http_host_state new_s = http_parse_host_char(s, *p);

        if (new_s == s_http_host_dead) {
            return 1;
        }

        switch (new_s) {
        case s_http_host:
            if (s != s_http_host) {
                u->field_data[UF_HOST].off = p - buf;
            }
            u->field_data[UF_HOST].len++;
            break;

        case s_http_host_v6:
            if (s != s_http_host_v6) {
                u->field_data[UF_HOST].off = p - buf;
            }
            u->field_data[UF_HOST].len++;
            break;

        case s_http_host_v6_zone_start:
        case s_http_host_v6_zone:
            u->field_data[UF_HOST].len++;
            break;

        case s_http_host_port:
            if (s != s_http_host_port) {
                u->field_data[UF_PORT].off = p - buf;
                u->field_data[UF_PORT].len = 0;
                u->field_set |= (1 << UF_PORT);
            }
            u->field_data[UF_PORT].len++;
            break;

        case s_http_userinfo:
            if (s != s_http_userinfo) {
                u->field_data[UF_USERINFO].off = p - buf;
                u->field_data[UF_USERINFO].len = 0;
                u->field_set |= (1 << UF_USERINFO);
            }
            u->field_data[UF_USERINFO].len++;
            break;

        default:
            break;
        }
        s = new_s;
    }

    /* Make sure we don't end somewhere unexpected */
    switch (s) {
    case s_http_host_start:
    case s_http_host_v6_start:
    case s_http_host_v6:
    case s_http_host_v6_zone_start:
    case s_http_host_v6_zone:
    case s_http_host_port_start:
    case s_http_userinfo:
    case s_http_userinfo_start:
        return 1;
    default:
        break;
    }

    return 0;
}

void http_parser_url_init(struct http_parser_url* u)
{
    memset(u, 0, sizeof(*u));
}

int http_parser_parse_url(const char* buf, size_t buflen, int is_connect, struct http_parser_url* u)
{
    enum state s;
    const char* p;
    enum http_parser_url_fields uf, old_uf;
    int found_at = 0;

    u->port = u->field_set = 0;
    s = is_connect ? s_req_server_start : s_req_spaces_before_url;
    old_uf = UF_MAX;

    for (p = buf; p < buf + buflen; p++) {
        s = parse_url_char(s, *p);

        /* Figure out the next field that we're operating on */
        switch (s) {
        case s_dead:
            return 1;

        /* Skip delimeters */
        case s_req_schema_slash:
        case s_req_schema_slash_slash:
        case s_req_server_start:
        case s_req_query_string_start:
        case s_req_fragment_start:
            continue;

        case s_req_schema:
            uf = UF_SCHEMA;
            break;

        case s_req_server_with_at:
            found_at = 1;

        /* FALLTHROUGH */
        case s_req_server:
            uf = UF_HOST;
            break;

        case s_req_path:
            uf = UF_PATH;
            break;

        case s_req_query_string:
            uf = UF_QUERY;
            break;

        case s_req_fragment:
            uf = UF_FRAGMENT;
            break;

        default:
            assert(!"Unexpected state");
            return 1;
        }

        /* Nothing's changed; soldier on */
        if (uf == old_uf) {
            u->field_data[uf].len++;
            continue;
        }

        u->field_data[uf].off = p - buf;
        u->field_data[uf].len = 1;

        u->field_set |= (1 << uf);
        old_uf = uf;
    }

    /* host must be present if there is a schema */
    /* parsing http:///toto will fail */
    if ((u->field_set & (1 << UF_SCHEMA)) && (u->field_set & (1 << UF_HOST)) == 0) {
        return 1;
    }

    if (u->field_set & (1 << UF_HOST)) {
        if (http_parse_host(buf, u, found_at) != 0) {
            return 1;
        }
    }

    /* CONNECT requests can only contain "hostname:port" */
    if (is_connect && u->field_set != ((1 << UF_HOST) | (1 << UF_PORT))) {
        return 1;
    }

    if (u->field_set & (1 << UF_PORT)) {
        uint16_t off;
        uint16_t len;
        const char* p;
        const char* end;
        unsigned long v;

        off = u->field_data[UF_PORT].off;
        len = u->field_data[UF_PORT].len;
        end = buf + off + len;

        /* NOTE: The characters are already validated and are in the [0-9] range */
        assert(off + len <= buflen && "Port number overflow");
        v = 0;
        for (p = buf + off; p < end; p++) {
            v *= 10;
            v += *p - '0';

            /* Ports have a max value of 2^16 */
            if (v > 0xffff) {
                return 1;
            }
        }

        u->port = (uint16_t)v;
    }

    return 0;
}

void http_parser_pause(http_parser* parser, int paused)
{
    /* Users should only be pausing/unpausing a parser that is not in an error
     * state. In non-debug builds, there's not much that we can do about this
     * other than ignore it.
     */
    if (HTTP_PARSER_ERRNO(parser) == HPE_OK || HTTP_PARSER_ERRNO(parser) == HPE_PAUSED) {
        SET_ERRNO((paused) ? HPE_PAUSED : HPE_OK);
    } else {
        assert(0 && "Attempting to pause parser in error state");
    }
}

int http_body_is_final(const struct http_parser* parser)
{
    return parser->state == s_message_done;
}

unsigned long http_parser_version(void)
{
    return HTTP_PARSER_VERSION_MAJOR * 0x10000 | HTTP_PARSER_VERSION_MINOR * 0x00100 | HTTP_PARSER_VERSION_PATCH * 0x00001;
}
